Rous sarcoma virus 35S RNA has been shown to have a terminally repeated nucleotide sequence of 21 residues. The presence of an identical nucleotide sequence at both ends of the viral RNA suggests a mechanism for reverse transcription of linear viral RNA into circular proviral DNA. Sequence analysis studies will be conducted to determine if reverse transcription of the viral RNA into cDNA proceeds in an ordered linear fashion by jumping from the 5' end of the template RNA to the 3' end. The possibility that the terminally redundant sequence in the viral RNA is also the integration site sequence will be examined by means of hybridization methods. Chemical synthesis of an icosadeoxyribonucleotide by triester methods containing the repeated nucleotide sequence is planned. This molecule will be used to detect and isolate RSV integration sites in chicken DNA. Sequence analysis of host cell DNA flanking the integration site will be conducted. These sequencing studies may reveal potential regulatory nucleotide sequences involved in expression of integration provirus genes.